local tab = {  
            0x00000000, 0x77073096, 0xee0e612c, 0x990951ba,  
            0x076dc419, 0x706af48f, 0xe963a535, 0x9e6495a3,  
            0x0edb8832, 0x79dcb8a4, 0xe0d5e91e, 0x97d2d988,  
            0x09b64c2b, 0x7eb17cbd, 0xe7b82d07, 0x90bf1d91,  
            0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,  
            0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7,  
            0x136c9856, 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec,  
            0x14015c4f, 0x63066cd9, 0xfa0f3d63, 0x8d080df5,  
            0x3b6e20c8, 0x4c69105e, 0xd56041e4, 0xa2677172,  
            0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,  
            0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940,  
            0x32d86ce3, 0x45df5c75, 0xdcd60dcf, 0xabd13d59,  
            0x26d930ac, 0x51de003a, 0xc8d75180, 0xbfd06116,  
            0x21b4f4b5, 0x56b3c423, 0xcfba9599, 0xb8bda50f,  
            0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,  
            0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d,  
            0x76dc4190, 0x01db7106, 0x98d220bc, 0xefd5102a,  
            0x71b18589, 0x06b6b51f, 0x9fbfe4a5, 0xe8b8d433,  
            0x7807c9a2, 0x0f00f934, 0x9609a88e, 0xe10e9818,  
            0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,  
            0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e,  
            0x6c0695ed, 0x1b01a57b, 0x8208f4c1, 0xf50fc457,  
            0x65b0d9c6, 0x12b7e950, 0x8bbeb8ea, 0xfcb9887c,  
            0x62dd1ddf, 0x15da2d49, 0x8cd37cf3, 0xfbd44c65,  
            0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,  
            0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb,  
            0x4369e96a, 0x346ed9fc, 0xad678846, 0xda60b8d0,  
            0x44042d73, 0x33031de5, 0xaa0a4c5f, 0xdd0d7cc9,  
            0x5005713c, 0x270241aa, 0xbe0b1010, 0xc90c2086,  
            0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,  
            0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4,  
            0x59b33d17, 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad,  
            0xedb88320, 0x9abfb3b6, 0x03b6e20c, 0x74b1d29a,  
            0xead54739, 0x9dd277af, 0x04db2615, 0x73dc1683,  
            0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,  
            0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1,  
            0xf00f9344, 0x8708a3d2, 0x1e01f268, 0x6906c2fe,  
            0xf762575d, 0x806567cb, 0x196c3671, 0x6e6b06e7,  
            0xfed41b76, 0x89d32be0, 0x10da7a5a, 0x67dd4acc,  
            0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,  
            0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252,  
            0xd1bb67f1, 0xa6bc5767, 0x3fb506dd, 0x48b2364b,  
            0xd80d2bda, 0xaf0a1b4c, 0x36034af6, 0x41047a60,  
            0xdf60efc3, 0xa867df55, 0x316e8eef, 0x4669be79,  
            0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,  
            0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f,  
            0xc5ba3bbe, 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04,  
            0xc2d7ffa7, 0xb5d0cf31, 0x2cd99e8b, 0x5bdeae1d,  
            0x9b64c2b0, 0xec63f226, 0x756aa39c, 0x026d930a,  
            0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,  
            0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38,  
            0x92d28e9b, 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21,  
            0x86d3d2d4, 0xf1d4e242, 0x68ddb3f8, 0x1fda836e,  
            0x81be16cd, 0xf6b9265b, 0x6fb077e1, 0x18b74777,  
            0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,  
            0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45,  
            0xa00ae278, 0xd70dd2ee, 0x4e048354, 0x3903b3c2,  
            0xa7672661, 0xd06016f7, 0x4969474d, 0x3e6e77db,  
            0xaed16a4a, 0xd9d65adc, 0x40df0b66, 0x37d83bf0,  
            0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,  
            0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6,  
            0xbad03605, 0xcdd70693, 0x54de5729, 0x23d967bf,  
            0xb3667a2e, 0xc4614ab8, 0x5d681b02, 0x2a6f2b94,  
            0xb40bbe37, 0xc30c8ea1, 0x5a05df1b, 0x2d02ef8d  
}  
  
local function xor(a, b)  
    local calc = 0      
  
    for i = 32, 0, -1 do  
    local val = 2 ^ i  
    local aa = false  
    local bb = false  
  
    if a == 0 then  
        calc = calc + b  
        break  
    end  
  
    if b == 0 then  
        calc = calc + a  
        break  
    end  
  
    if a >= val then  
        aa = true  
        a = a - val  
    end  
  
    if b >= val then  
        bb = true  
        b = b - val  
    end  
  
    if not (aa and bb) and (aa or bb) then  
        calc = calc + val  
    end  
    end  
  
    return math.floor(calc)  
end  
  
local function lshift(num, left)  
    local res = num * (2 ^ left)  
    return res % (2 ^ 32)  
end  
  
local function rshift(num, right)  
    local res = num / (2 ^ right)  
    return math.floor(res)  
end  
  
local CRC32 = {}  
  
function CRC32.hash(str)  
    local count = string.len(str)  
    local crc = xor(0,0xFFFFFFFF)  
    for i=1,count do  
        local byte = string.byte(str, i)  
        local a = rshift(crc,8) & 0x00FFFFFF  
        local b = tab[(xor(crc,byte) & 0xFF)+1]  
        crc =  xor(a , b)  
    end  
    crc = xor(crc , 0xFFFFFFFF)  
    crc = crc | -(crc & lshift(1,31))  
      
    crc = crc & 0xFFFFFFFF  
      
    return crc
end

------------------------------------------------------------------
--测试
------------------------------------------------------------------
if arg and arg[0] == "crc32.lua" then
    local old_time = os.time()
    local crc = CRC32
    local res = crc.hash("aaaaaa")
    print(string.format("0x%x",tonumber(res)), type(res))
    print("use time:",os.time() - old_time)

end



return CRC32  